1. Field of the Invention
The present invention relates to a silver halide color photographic material. More particularly, the present invention relates to a silver halide color photographic material that employs a thinner coating format to achieve higher image sharpness and which yet produces an effectively recolored cyan dye image while ensuring improved stability under varying processing conditions as well as good storage characteristics.
2. Description of the Prior Art
Modern light-sensitive materials are required to meet the growing demand of the user for higher image quality. On the other hand, active efforts have been made to reduce the size of the format of light-sensitive materials. For these two reasons, a multitude of proposals have been made for making light-sensitive materials capable of producing images of high quality.
The quality of the image produced by a color light-sensitive material is generally evaluated in terms of sharpness, graininess and color reproduction. A particularly high degree of sharpness is required in order to realize the reproduction of fine detail in a light-sensitive material of small format.
The efforts which have been made to provide improved image sharpness are based on two approaches, optical and chemical (i.e., rapid development). In the optical approach, the use of monodispersed silver halide grains has atracted the attention of researchers because they contribute to enhanced transmittance of radiation. Efforts also continue to decrease optical scattering by making emulsion layers as thin as possible. Light is scattered progressively further as it penerates deeper into a multilayer structure, so that the image formed in a silver halide emulsion layer which is closer to the support tends to be less sharp than the images formed on the overlying layers. It is therefore known that a particularly effective way to provide improved image sharpness is to make the emulsion layers thinner by reducing the binder content [see, for example, Journal of the Optical Society of America 58 (9), 1245-1256 (1968) and Photographic Science and Engineering 16 (3), 181-191 (1972)]. The specific means that have been proposed for meeting this need include reduction in the coating weight of gelatin, reduction in the coating weight of coupler, reduction in the amount of a high-boiling point solvent used as a coupler dispersant, and the use of a "polymer coupler". However, none of these methods are desirable for the purpose of attaining improved photographic performance since they increase the graininess and degrade the storage stability and the ability of couplers.
For instance, if the approach selected is simply to reduce the thickness of a gelatin coating in a light-sensitive layer with a high-boiling point organic solvent being used as a coupler solvent, undesirable phenomena such as the agglomeration and disruption of coupler in oil droplets in the coating occur and this causes either the crystallization of the coupler or the "bleeding" of oil droplets on the surface of the light-sensitive material. Because of these disadvantages, the method of simply reducing the coating weight of gelatin has yet to be commercialized.
The reduction in the amount of coupler used generally results in a lowered color density and the development of couplers capable of efficient color formation is strongly desired. In ordinary color light-sensitive materials, the red-sensitive emulsion layer which is situated the closest to the support of the emulsion layers is most susceptible to the effects of development and hence are highly likely to experience a considerable drop in color density as a result of the reduced use of a coupler. The advent of a cyan coupler capable of efficient color formation is therefore desired.
In order to meet the requirement for rapid development, the tendency of modern photographic laboratories to employ higher processing temperatures and shorten the processing period is increasing. However, if an attempt is made to shorten the step of bleaching or bleach-fixing developed silver in a color light-sensitive material that employs a conventional naphtholic cyan coupler, a serious problem occurs in that the cyan dye is reduced by a large amount of ferrous ions to produce a faded image.